1. Field of the Invention
The present invention relates generally to repair techniques for a motor vehicle bodywork. More particularly, the invention relates to a method or apparatus for replacement of an aluminum bearer at a longitudinal bearer joint in a vehicle bodywork.
2. Description of the Prior Art
From published European Patent document EP-PS 0 146 716, it is known how to produce the load-bearing structure of a vehicle bodywork by using nodal connector elements for joining together hollow section bearers. Extruded aluminum sections are used as the hollow section bearers and cast aluminum joint pieces are used as the nodal connector elements.
In the familiar longitudinal bearer design of a vehicle frame disclosed in German Patent document DE-OS 37 40 402, the longitudinal bearers are partitioned before the assembly is suspended in place. Here again, the forward most portion of the longitudinal bearer is fashioned as a plurality of joined together deformation elements, so that they are more easily deformed than the adjacent rearward portions of the longitudinal bearer. The longitudinal bearer comprises a plurality of bearer segments, arranged in succession, and which are connected together at abutting ends or bearing surfaces. The abutting bearing surfaces are designed as rotational surfaces in the transverse direction. A central, axially aligned connection is used to join the abutting bearing surfaces together.
This configuration is especially advantageous when the bearer segments are formed as extruded aluminum sections, since the easily accessible bolt connection permits quick and simple replacement of a forward deformed longitudinal bearer piece after a minor collision. Also, the strength loss problems associated with the replacement of aluminum welds does not occur. However, the costs of such bolt connections are relatively high.
It is also known from the prior art how to construct a hollow-section longitudinal bearer assembly of a vehicle frame from a plurality of deformable longitudinal bearer segments. These individual longitudinal bearer segments are joined together, in end to end fashion, by a surrounding weld beginning with the forward most segment and working rearwards. Each succeeding longitudinal bearer segment is dimensioned with a progressingly greater wall thickness and/or are made of a progressively higher grade of material than its preceding bearer segment so that the resulting longitudinal bearer assembly has a resistance to deformation which increases toward the middle of the vehicle. This provides for a graduated resistance to deformation up to the middle of the vehicle so that in the event of a minor accident, only one or two of the forward most longitudinal bearer segments will deform without damage to the adjacent successive (rearward) bearer segments depending on the severity of the accident. This arrangement greatly facilitates the repair of the vehicle front end since only the deformed segments need replacement and this arrangement also avoids an undesirable total deformation of the vehicle frame in less severe accidents.
In the vehicle frame of the type described, replacement of the deformed longitudinal bearer segments involved is accomplished by cutting out the damaged segments and welding on new bearer segments. For the case where the longitudinal bearer comprises of sheetmetal segments, this repair procedure does not give rise to any major structural problems since the original strength of the sheet metal is substantially retained even after welding.
It is also well known in the art to provide a connection for a longitudinal bearer in a vehicle body wherein an aluminum bearer is formed as an extruded section and is inserted into a tubular aluminum recess of a cast metal piece. The aluminum bearer is then welded to the front edge of this tubular recess by a surrounding weld seam. Such a connection is stable and economical.
However, it is commonly known that the thermal welding of heat treatable aluminum alloys produces a significant decrease in the strength in the material in the so-called "zone of thermal influence" immediately adjacent the weld zone. A surrounding weld connection, as is used in the above-described bearer joint, is especially critical, since it produces a weakening in a continuous transverse plane. The decrease in strength of a first bearer joint and a first welding procedure can be factored into the dimensions. However, in view of the related welding procedure required in the typical replacement of bearers whereby the weld seam is first cut out and a new bearer piece is then inserted and welded to the front edge of the tubular recess, there is a resulting uncontrollable damage to the grain texture and a correspondingly large decrease in strength in the material and danger of fracture during heavy load conditions.
This is particularly problematic in the situation where the member is connected to a divided longitudinal bearer, since in this situation it is taken for granted that the more easily deformed forward sections of the longitudinal bearer assembly will necessarily be replaced during repairs after an accident, and perhaps may even need to be replaced at least once for normal wear or fatigue during the lifetime of the vehicle. The welding procedures repeatedly required in this case would unacceptably weaken the joint by progressive structural change in the zone of thermal influence of the material of the aluminum alloy.
While it is conceivable to incorporate an acceptable safety factor in the initial design such that the joint is sufficiently thick in the first instance so that even the aforesaid severe decrease in strength caused by successive welding procedures does not result in danger of fracture, this is not a practical solution for reasons of cost and weight. Furthermore, it is desirable to provide the customer with a vehicle body which retains its the original strength even after repairs.